Animal models of human disease constitute an indispensable modality for Center Investigators. Studies of liver cell transplantation, gene therapy and hepatic pathophysiology remain a major focus of the Center. The Core continues to thrive under Dr. Gupta's expert direction, which is entering its second decade. During the previous funding periods, the Core provided its services to Center Investigators, as well as to investigators outside of the Liver Center and the College of Medicine. The animals provided by the Core facilitate studies concerning development of therapies for metabolic deficiency states, genetic liver disease, and acute or chronic liver failure. In addition, animals provided facilitate studies of hepatic gene expression, progenitor cell and stem cell biology, and liver growth control. Although many studies are performed in vitro, use of well-characterized animal models with unique genetic characteristics has been invaluable and will remain so in the future. The mission of the Animal Core is to breed, maintain and provide specific animals that are not at all available or readily available elsewhere. The Core offers instructional services by training Investigators or designees in the performance of specific animal procedures. Consultation is provided in experimental design concerning specific animal studies. Novel animal models are developed with the assistance of Core resources for advancing various relevant studies, e.g., radiolabeling of specific liver cell types for biodistribution analysis, and generation of new animal models for identifying transplanted cells. The Core remains a most dynamic force with additions and deletions in its stock according to Center requirements. In the current period, we expect that the Core will continue to provide animals in its repertoire to qualified Investigators, reproduce animal models under request, and train Investigators in animal procedures as necessary. New Investigators are especially encouraged by the Core to use its resources. Furthermore, the Core attempts to incorporate new services, e.g., harvesting and freezing of embryos from unique animals will be added as a new Core service during this period of funding, such that animal colonies could be discontinued if necessary and animals could be rederived in case of natural disasters (infection, loss of fecundity, etc).